PICTURES ARE REPRESENTATIVE OF ITEM, BUT ARE NOT OF THE ACTUAL ITEM. Product dimensions, finish, head markings, thread length, stamping shape or forging shape, etc., may differ from picture. Products are guaranteed to meet the specifications to which they are manufactured. Specifications allow for tolerances in dimension and shape, which can vary from lot to lot. A straight shank fastener with external threads designed to go through a hole or nut that is pre-tapped to form a mating thread for the screw. Machine screws form a fastening superior in strength to spaced thread screws.. STEEL: Steel Zinc is the most common and most popular variety of steel machine screws. Steel Zinc yellow screws are popular in electronics applications. Steel Zinc Black and Black Oxide screws are used to blend in with black-colored components.. STAINLESS: 18-8 Stainless steel machine screws are used in applications which require general atmospheric corrosion resistance, in food processing machinery and refrigeration equipment. Stainless is also superior to steel in withstanding some elevation in application operating temperature while maintaining its strength. 316 Stainless steel offers superior corrosion resistance to 18-8 and is superior at maintaining its strength at high temperatures.. 410 Stainless steel is recommended in applications where greater tensile strength is needed such as control mechanisms or valves under high stress. 410 is not as corrosion resistant as are 18-8 or 316 stainless.. ALUMINUM: In some applications, aluminum machine screws can be a less expensive alternative to stainless screws because of their resistance to corrosion and high rate of conductivity. Aluminum machine screws should be fastened with aluminum nuts to minimi.